Dental implants are commonly used in today's dental practices to support various prostheses. Challenges to the successful placement of dental implants include poor bone quality and various hidden anatomical features such as nerves, roots, and sinus cavities. Surgical preplanning methods and drill guide apparatuses may be used to better address these challenges. With edentulous cases, surgical drill guide apparatuses can be divided into two categories: bone borne surgical drill guides and gum tissue borne surgical guides.
Bone borne surgical drill guides are made to fit on a patient's jawbone, and can be made from either a digital jawbone model or rapid-prototyped physical jawbone model of the patient. The primary problem with bone borne surgical guides is the invasiveness of the amount of flapping of the gum tissue that the surgeon has to create in order for the guide to fit correctly on the patient jawbone. The amount of flapping required increases the likelihood of surgical risks and complications, including blood loss, infection, healing problems, and overall pain experienced by the patient. Flapping and suturing also requires a great deal of surgical time. In addition to the problems associated with the surgical procedure, difficulties may also arise when the jawbone has low density, which happens often with Maxilla bones in posterior region. Low bone density makes it difficult to define the contour of the bone in CT images, which may cause the bone borne surgical drill guide to fit poorly. Thus, the use of bone borne surgical drill guides has drawbacks and it would be preferred to overcome their associated problems.
Gum tissue borne surgical drill guides are made to fit on top of a patient's gum tissue without the need for any surgical incisions to stabilize the guide. In order to create this type of surgical guide, the surface scan data of the gum tissue and the tomography data of the jawbone need to be accurately aligned and mapped. For this purpose, usually an imaging template is worn by the patient during tomography scanning, and the fiducial markers on the device are used for alignment of the different data sets. While this method is less surgically invasive than the bone borne method, gum tissue borne surgical guides lack stability. Gum tissue is in a constant state of movement and drift, and is also pliable with pressure. Moreover, certain health conditions and even the intake of certain foods make gum tissue more prone to swelling. These conditions may prevent the accurate positioning of the device in the mouth. Here, even if the surgeon uses anchor screws, they may be securing the device in the wrong position. This type of surgical drill guide sacrifices accuracy for convenience. Thus, it would be preferred to overcome these problems.
Accordingly, it would be desirable to provide a stable and accurate surgical drill guide apparatus that requires only minimum flapping and fits to both gum tissue and one or multiple small areas of jawbone. Such apparatus may increase the stability of the surgical guide by clasping and/or contacting the jawbone, while improving the overall fit and minimizing the need of flapping by also clasping and/or contacting selected areas of the gum tissue at the same time. The apparatus may be configured to accurately place dental implants according to the planned positions.
It would also be preferable to provide an apparatus that may be custom designed to suit the unique anatomical features of each individual. The device may be designed on a digital anatomical jawbone model with accurately mapped and aligned gum tissue information, and may be rapid prototyped or milled as a drill guide frame or frame set. Also, the apparatus may be made by hand on the rapid prototyped or CNC milled physical anatomical model that partially exposes the jawbone structure.
Currently, the most common way of taking a positional index of installed implants is by taking a dental impression. Right after the placement of implants or after the integration of implants, impression copings are placed on the installed implants and a dental impression is taken using an impression tray and one or more dental impression materials. For more accuracy with fully edentulous cases with multiple implants, it is recommended that the impression copings are splinted with some rigid materials before the impression is taken. Then a new master dental model is created from the impression in a traditional way, using implant analogs. Because of the stress applied on the impression copings and material distortion by the impression materials and impression tray, a verification jig should be made to verify the model and, if the gum tissue contour is altered, a new impression will be taken after it is healed. Alternatively, instead of a physical impression, the positions of installed implants may be recorded by surface scanning the patient's mouth with an intraoral scanner, and a new master dental model can be produced by rapid prototyping.
However, with either method, if the contour of the gum tissue is altered by dentition extraction, bone adjustment, or bone grafting, preoperative information such as the bite registration, existing prosthesis, and natural dentition before extraction, can no longer be used in order to articulate the new master dental model to the opposing jaw model. This is the case with a majority of edentulous flap surgeries, and, if so, the dental practitioner must go through another cumbersome set of procedures of taking a new bite registration since the information is essential for creation of a new prosthesis. This will most likely cause multiple adjustments back and forth between the dental practitioner and the dental laboratory because creating a full mouth prosthesis without the previous bite information can be a very difficult task once the information is lost. The teachings herein help to solve these and other problems.
Preoperative Data File and Creation of Guide Appliances
According to an illustrative approach, the master data file may be created with the data sets incorporating one or more surface and/or tomography scans of a patient's mouth, digital topography data of the patient's existing fixed or removable prosthesis, digital topography data of the dental impression, digital topography data of the dental cast, and other related preoperative information such as bite registration, oriented to each other with coordinates defined by at least one natural or artificial reference marker that exists under and is both fixed constant between the data sets. A natural reference marker refers to a pre-existing oral structure while an artificial reference marker refers to a marker inserted into a patient's mouth, but consistently fixed at the same coordinate location within the mouth after each insertion. In either case, for a reference marker its coordinates are consistent and do not change between scannings. A digital dental anatomical diagnostic model such as a digital preoperative master dental model (the ‘digital preoperative model’) may be created using the data in the master data file, and a multiple-piece stackable surgical guide set (the ‘surgical guide set’) may be designed using this digital preoperative model. Then the design of the surgical guide set is stored within the master data file and all the sections of the surgical guide set can be manufactured by rapid prototyping. The surgical guide set may include a base frame and one or more attachable/detachable superstructures such as a surgical drill guide section, transfer appliance section and temporary prosthesis section. There are mainly two different ways of taking a positional index of installed implants back to the preoperative model although there are many variations within these processes. One way is to take a digital positional index of installed implants and the other way is to take a physical positional index of installed implants. Both processes use a section of the surgical guide to connect the new information to the preoperative information.
Process of Taking a Digital Positional Index of the Installed Implants
If a dental practitioner chooses to take a digital positional index of the newly installed implants with an intraoral scanner, the base frame of the above surgical guide set can be utilized as a fiducial marker linkable to the digital preoperative model. After placement of dental implants represented in part by a fixed implant head extending outwardly from a body surface within a patient's mouth to hold various implant components, the surgical guide section may be removed from the base frame but the base frame will remain in the mouth. The base frame has a wide enough opening around the area of surgical sites so that the implant heads of dental implants are visible but not touching the base frame. Utilizing an intraoral scanner, the base frame may be scanned along with the implant heads. Now, the implant heads are indexed to the base frame within the scan data. The scan data can be then superimposed onto the digital preoperative model in the master data file by aligning the base frame portion of the scan data to the design of the base frame inside of the master data file already oriented to the digital preoperative model. The position of the installed implant heads, which are oriented to the base frame within the intraoral scan data, will be oriented to the digital preoperative model as well by this alignment, creating a digital postoperative dental model with installed implants' positions and angulations.
If a required implant head is not visible enough above the patient's oral structure, corresponding implant components such as a scan body, impression coping, and temporary abutment may be placed on the implants during the postoperative scan. Just like the currently used digital impression method, this method will allow the surgeon to take an index of the installed implants without applying physical stress on the implants or worrying about impression materials getting underneath the open gum tissue, but, unlike the currently used method, this method allows the dental practitioners and lab technicians to transfer the positional information of installed implants back to the digital preoperative model, to which other essential preoperative information may have been already oriented.
Process of Taking a Physical Positional Index of the Installed Implants
If a dental practitioner chooses to take a physical positional index of the patient's mouth, a superstructure of the surgical guide set can be utilized as a transfer jig. The superstructure that can be used as a transfer jig may include a specifically designed transfer jig appliance, a temporary prosthesis, and a surgical guide section. At the surgery, after a dental implant(s) are installed, corresponding implant components can be connected to the head of the installed dental implant; the implant head is usually the only visible portion of an implant and implant components are generally attached only to the head of the implant. Then the implant component may in turn be fixated to the superstructure used as a transfer jig by an adhesive material. If a transfer jig appliance (or temporary prosthesis) is used to take a physical positional index, the surgical guide can be removed from the base frame after installing implants and transfer jig appliance can be attached to the base frame and then connected to the implant components. Once this is done, the implant components can be detached from the implant heads with the superstructure (used as a transfer jig appliance) and base frame then removed from the mouth. Subsequently, the installed implants' positional information captured by the transfer attachment or the surgical guide section can be transferred back to either a digital or physical preoperative model, also called anatomical diagnostic models herein, in order to convert the preoperative model into the postoperative dental model taking into account the actual position of installed dental implant.
If the information is to be transferred to the digital preoperative model, the corresponding implant components attached to the transfer appliance (a superstructure used as a transfer jig) can be surface scanned either with a desktop surface scanner or hand held surface scanner. Now, the scan data contains the implant components indexed to the transfer appliance. The scan data can be then superimposed onto the digital preoperative model in the master data file by aligning the superstructure portion of the scan data to the design of the superstructure inside of the master data file already oriented to the digital preoperative model. The position of the implant components will be oriented to the digital preoperative model as well by this alignment, creating a digital postoperative dental model with installed implants' positions and angulations.
Alternatively, a physical preoperative model can be manufactured from the digital preoperative model by rapid prototyping and positional information of the installed dental implants can be transferred to the physical model by placing the surgical guide set along with the attached impression copings on the physical model.
As the base frame remains in the set position before and after the placement of implants at the surgery, all the superstructures including a transfer attachment will retain the same orientation as they were designed on the preoperative model. Thus, the information obtained by this method is transferable back to the physical or digital preoperative model. Additionally, if this method is used, the surgeon can save time on splinting the implants, and does not have to use an impression material to capture the impression of surrounding gum tissue along with the impression copings since the preoperative model has the all the obtainable information already. This will significantly reduce stress on the impression copings and connected implants.
Overview of the Two Illustrative Approaches of Combining the Postoperative Data Files and the Preoperative Data Files and Some of their Advantages
The illustrative approaches have significant advantages over conventional teachings. For example, by using a section of the surgical guide set, a postoperative positional index of installed implants will become transferrable and linkable to the digital or physical preoperative model. Since all sections of the surgical guide set are created on the digital preoperative model within the master data file and the design of each section is stored with coordinates to the digital preoperative model, the scan image of each section can be perfectly aligned with its design already oriented to the digital model. Additionally, if a physical preoperative model is manufactured from the digital preoperative model, the implant components attached to a transfer attachment can be transferrable to the physical preoperative model because the surgical guide set is designed to fit both the patient's mouth and the preoperative model. This way, dental practitioners and lab technicians will be able to make full use of other preoperative information oriented to the digital or physical preoperative model, sparing them from time and trouble to re-obtain critical information, such as the bite registration and a contour of an ideal prosthesis. By bridging the preoperative information and postoperative information, a seamless workflow from the surgery to fabrication of a prosthesis is established. Taking a positional index of installed implants and creating the postoperative master model are much easier, and a new implant prosthesis can be created without numerous adjustments that may be required using conventional teachings.